As Super Bowl XLVIII fades into the history books (hopefully never again to be so lop-sided a defeat), another game is quietly gaining steam as the place to be for the most avid sports fanatics. DraftKings, a leader in online fantasy sports games, has seen its customer base, daily engagement, and giveaway prize totals surge almost as quickly as the Seattle Seahawks have transformed themselves into Super Bowl champions.

Launched in 2012, DraftKings paid out $50 million in prizes in 2013 to thousands of players who excelled in weekly fantasy football, daily fantasy baseball, daily fantasy basketball and daily fantasy hockey. In just the last four months, the Boston-based upstart’s user base has grown fourfold, with nearly 50,000 active daily users and as many as one million registered players. Even better, DraftKings users spend an average of more than two hours every day on the site.

All this before the company’s new mobile app was launched a few weeks ago and new games, such as golf, were added to the existing stable of sports. CEO Jason Robins says his company is poised to blow past these impressive numbers in 2014, thanks to more aggressive marketing and a slew of product enhancements.

With just 32 employees thus far, accomplishing so much so quickly is no easy feat. In a candid interview, Robins opens up about what he believes has been key to DraftKings high-octane growth and about the unique challenges that lie head.

Q: What has been your formula for success?

A: We have spent a lot of time focusing on the brand and the customer experience. Three things have been key: For the customer, we want everything to be fun, easy to use, and engaging. We look at a lot of metrics for every feature we roll out. We see what’s working and what isn’t by testing everything with a group of customers.

Q. Can you give an example of how that has worked?

A. In the beginning of the NFL season, we launched a feature so people could send private challenges to friends. The social aspect of fantasy sports is huge and we needed to provide an easier way for people to play against their friends. After launching the feature, we found that a lot of challenges were not getting accepted. We wanted to know why and figured out that a lot of challenges were being lost in people’s email inbox.. At the same time, many of these same people were coming to our website without knowing about the challenges their friends were sending.

So we launched a new system of notifications on our website so people could see an alarm bell that shows a challenge. As soon as we launched this feature, our declines of challenges went down—70% on the first day. We will soon launch a push notification on our mobile app, which should make it even better. If you are out and about, you will know when someone has challenged you to a game. In addition, we just launched a feature where you can reserve a seat for a game without having to pick your team right away. People know they want to play but maybe can’t pick their team at that time. So this lets them accept a friend’s challenge and then later set their lineup. We have seen another 45% drop in cancellations with that.

All this was about tackling one key metric: the cancellation rate of game challenges.

Q. What are some things that have surprised you in getting the business off the ground?

A. Sometimes we are surprised by how our users respond to new features. We launched something called Lineups, which is a way to easily manage your teams. If you create 40 different teams and have players across many games, it can be hard to manage when a key player you had on 30 teams suddenly is out because of an injury. Previously you would have to edit out that play in each game. Now you can get the guy out of your lineups automatically. We knew this would be popular but it has become one of the defining features of our product.

Another lesson we have learned is about marketing. I came from Vistaprint, which had success with digital marketing channels at an incredible level of scale before venturing into offline advertising. It took us awhile to realize that wouldn’t work for us at DraftKings. Broadcast marketing channels have been easier for us to scale than digital.

Q. Is it difficult to build a virtual business that is so dependent on the real world?

A. The beauty of sports is that you already start with a great product. It’s the world’s greatest reality show. We don’t have to create the content. It’s already there. For us, it’s more about how to add to an already interesting experience. Our app fits in particularly well. For example, if you are at a game, it can be a second-screen experience. It opens up a lot of different ways to add on to the experience.

Q. What have been some of the biggest challenges?

A. We are a product-focused culture and we always have to make sure we continue to pay as much attention to the technology and back-end operations. We have a very complicated product with constant transactions occurring. So the issue of security is always there and we have to have a really strong infrastructure that is error free. We can’t have people lose trust.

When we roll out a new feature, we make a list of all the negative things that could happen from launching the feature. Not just bugs but product design etc. We have to have an answer for each one or we don’t roll out the feature. We want to grow fast but there’s a lot of tricky stuff on the technical side.

Q. What keeps you up at night?

A. Staying ahead of the competition on the innovation front and making sure that everything we do is high quality. I also worry about hiring and retaining the best talent. It’s a little easier because of the business we are in. People feel a lot of passion for sports. It also helps being in Boston.

One of the most exciting aspects of venture investing is when we see a company that plays a role in creating a consumer phenomenon. DraftKings is just that sort of company. Founded only a year ago, DraftKings is a leader in the emerging space of real-time fantasy sports, awarding over $50 million in prizes this year in its first full year of operations.

For years, the conventional wisdom around fantasy sports leagues was that they represented a huge, growing, engaged audience, but without a clear path to monetization. Enter real-time, daily fantasy sports. Jason Robins, the founder and CEO of Draft Kings had the vision to remove the friction associated with fantasy sports, and provide a huge incentive to play. By changing the games to daily events rather than season-long events, Jason and the team at Draft Kings made fantasy sports more real-time and accessible, a valuable companion to the live sports viewing experience. Rather than joining one league for a whole season, players can now play multiple distinct games every day. Furthermore, by offering cash prizes to the winners of these daily fantasy games, Draft Kings solved the monetization challenge associated with fantasy sports.

The results have been nothing short of amazing. User growth and retention are both impressive. Over 75% of players that played a game in 2012 are active in 2013. Even more impressive, just since August of this year, Draft Kings has tripled its customer base with year-over-year revenue growth of over 10x.

We are excited to join Jason and his team at DraftKings to help redefine the fantasy sports market.